Decimal point processing system dealing with overflow

ABSTRACT

A decimal point processing system in a calculator capable of arbitrarily setting the decimal point position for the result of an operation within the range of digit indication positions given, and also of indicating, with priority, figures of the above n positions (n being the number of indication positions) being indicated.

United States Patent Kurokawa et al.

[ 51 Sept. 19, 1972 DECIMAL POINT PROCESSING SYSTEM DEALING WITH OVERFLOW [72] Inventors: Noriyuki Kurokawa; Hiroshi Minami, both of Funabashi, Japan [73] Assignee: Hitachi Ltd., Tokyo, Japan [22] Filed: May 21, 1970 [21] Appl. No.: 39,244

[30] Foreign Application Priority Data Primary ExaminerMalcolm A. Morrison Assistant Examiner--David H. Malzahn AttorneyCraig & Antonelli [57] ABSTRACT A decimal point processing system in a calculator May 23, 1969 Japan ..44/39594 capable of Setting the decimal point p [52] U S Cl 235/159 235/160 tion for the result of an operation within the range of [5'1] U (506i 7/38 digit indication positions given, and also of indicating, [58] Field 0rsrilj.1111...II1II..III.I5sYi3 160 164 with Priority, figures of the abQVe PositionS being the number of indication positions) being indicated.

[56] References Cited 10 Claims, 9 Drawing Figures UNITED STATES PATENTS 3,074,635 l/l963 Borne et a1. ..235/l56 SH/FT GATE CONTROL l' l l 1 W? r i I r J F45 R/ /?0 l DUECWO/V OF I 04 a I F145 0 l R2 DETECTION OF R/P 7 /4 I l R/P 1 COMPAR/SO/V OF L CLOCK CO/WPOL I R/P 2 AND ""---17 R/PLFP P2P PATENTED SE? 19 1912 SHEET 2 or a F/G. 2a

AFTER SETT/NG AETERDEC/MAL POI/V7 ADJUSTMENT AFTERADD/T/O/V AFTERPOS/fiO/VADJUSTME/VT TUPRESELECTEDPOS/flO/WH/V/SH) CO/Vl E/VT/O/VAL SYSTEM R/ [ND/CAT/ONFPEG/STER R2 1 AUX/L/ARYREG/STER PRESENT SYSTEM A PRESELECTED DEC/MAL PO/N T POS/ 7'/0/V INVENTORS NORNUKI KUROKAWA, AND Hmosm Ml NAMi BY finfingui, Shaun- 1' HKH ATTORNEYS SHEET 3 BF 8 AFTER SETT/NG AFTER DEC/MAL F0//vT ADJUSTMENT 0VE/?FLOW AFTER ADD/T/O/V AFTER POSITION ADJUSTMENT T0 PRESELECTED Fos/r/o/v 1 F/N/SH 1 A I A CONVENTIONAL PREsE/vT SYSTEM SYSTEM INVENTORS NORIIUK\ KuRokAwA AND Hmosm MINAMI BY C-vuig, qnkmnui, StevJQvt ATTORNEYS PATENTED 19 I973 3.692.990

SHEEIUUF8 AFTER SETT/ S A I A AFTER DEC/MAL POI/V7 ADJUSTMENT --0VE1?FL0W AFTER ADD/T/ON AFTER R0S/T/0/v ADJUSTMENT 70 RRESEL E6750 F0S/T/0/v 1 F/M/SH 1 R2345678.9000OO0O l2345678.9000OO CONVENT/ONAL PRESENT SYSTEM SYSTEM INVENTORS NORIYUKI KuRbKnwn n50 HIROSHI 11114111191 PAIENTEB SEP 19 1972 SHEET S [If 8 FIG. 20'

AFTERSETT/NG AFTEROEC/MAL POINT ADJUSTMENT AFTERADD/T/O/V F I 7 5| 0 00000035 345 s 7 :1 0000 0003 5 345 s 7 0vE/7FL0w I R2 999 9 9 99 23 45 5 7 9 999 9 99. I 23 4 5 5 7 C0/vvE/vT/0NAL SYSTEM IOOOOOOO.353456 PRESENT SYSTEM INVENTORS NORNUKI KuRoKa A mp HIROSHI MuuAm ATTORNEYS STEP 4 STEP 6 INVENTORS ATTORNEYS SHEET 8 0F 8 uoawum KUROKRWR AND HIROSHI MuNRMl BY Cvala, Rnknelli, gtgmmvtw Hi" PATENTED SEP 19 1912 FIG. 3a

FAS=O AND RI P #4 OVF RI XIO RIP-H END DECIMAL POINT PROCESSING SYSTEM DEALING WITH OVERFLOW BACKGROUND OF THE INVENTION:

1. FIELD OF THE INVENTION This invention relates to a decimal point processing system for use in electronic desk-top calculators.

2. DESCRIPTION OF THE PRIOR ART Among decimal point processing systems employed in conventional electronic desk-top calculators, there are fixed decimal point systems, automatic decimal point systems, etc. Since, however, they employ an overflow system in which a number of figures in excess of that over the digit indication positions overflows to the higher positions, there occur some cases according to the decimal point position of numbers in which the capacity of the digit indication positions of a calculator cannot be fully utilized.

Some special calculators for use in engineering calculations employ a floating decimal point system in which the decimal point position is indicated by an exponent. But this system has a drawback in that the decimal point position cannot be read out directly and is not suitable for ordinary business calculations.

In an automatic decimal point system capable of setting the decimal point position and frequently employed in recent electronic desk-top calculators, the decimal point position of a registered number is recorded in a counter or a register, and in the case of addition or subtraction, the decimal point positions of the addend and the augend are compared. The number having a lower decimal point position is then shifted to have the same decimal point position as the other, and after operation, the resultant number is displayed as a decimal number with its decimal point position adjusted at the preset position. Decimal point processing in multiplication and division is done in a similar way.

This system is superior to other systems in that the decimal point position can be read out easily since the decimal point position of the result of an operation can be set at any desired position, but also has the opportunity to invalidatethe operation by the overflow of the number.

SUMMARY OF THE INVENTION:

An object of the invention is to provide an improved automatic decimal point processing system capable of fully utilizing the capacity of the figure indication of a calculator. More particularly, this invention intends to derive effective results also for the conventionally invalid operations due to overflow, by displaying the upper n figures (n being the number of indication positions of a calculator) of the operation result.

The gist of the present invention is given in the following.

In the step of bringing the decimal point positions of the operands (the addend and augend in the case of addition) into coincidence after setting the operands in the registers, when the highest figure of an operand having a lower decimal point position is detected to exist in the highest position of the indication register, even if the coincidence of the decimal point positions has not yet been attained, the carry of the operand is interrupted and the number having a higher decimal point position is shifted to the lower positions instead of bringing the decimal positions of the operands into coincidence.

In the step of making the result of an operation take a preselected decimal point position, when the highest figure of the operation result is detected to exist in the highest position of the indication register, the carry of the result of an operation is interrupted even when the coincidence of the decimal point positions has not yet been attained.

In the course of an operation, when the result of an operation overflows from the register, the overflowed figure or figures are temporarily stored in another storage means, and the result of the operation is shifted to the lower positions by detecting the overflow so as to cut off the lower figures and to send back the overflowed figures to the indication register from the storage means.

As is described above, the invalidation of operations due to overflow is prevented by indicating the more significant higher order, figures of the result of an operation according to the invention. And the invalidation of an operation occurs only in such case when the integral figures of the result of an operation causes underflow.

Based on a similar principle, even when either of the registered operands causes overflow from the indication register, the overflowed figure or figures are termporarily stored in another storage means, and by detecting this state, the overflowed figures are sent back to the register by cutting off lower figures to eliminate overflow and hence the invalidation of an operation.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIGS. la and lb are block diagrams of operation systems according to the invention;

FIGS. 2a to 2d are diagrams showing in comparison how the content of a register varies according to the in vention and the conventional system; and

FIGS. 3a to 30 are flowcharts showing in comparison the decimal point processing according to the conventional system and the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

FIG. 1a illustrates an example of a two register system and FIG. lb relates to a three register system. In either of the examples, input numbers (operands) from the keyboard are introduced into registers from the lowest position according to the ordinary automatic decimal point system and the decimal point position is indicated by the number of positions below the decimal point.

In the case of addition in FIG. 1a, the augend is introduced into an indication register R1 and the addend is introduced to an auxiliary register R2. The contents of these registers are successively added in an adder FAS one by one and the result of the addition is applied to the indication register R1 from the highest position in place of the augend. The positions of the decimal points in the registers R1 and R2 are memorized in the respective decimal point registers RIP and R2P. The result of the operation contained in the indication register R1 and the accompanying point register RIP is sent to an indicator disposed separately and indicated thereat as a natural number by means known in the art. Reference R0 represents an auxiliary register of four bits, and G G and G designate shift gates.

The shift control of numerical information is performed in the indication register R1. Normally information circulates in the loop of Rl-G,-G -G -FAS-Rl. In the case of a shift to the right (figures going to lower positions), the circulation loop changes to Rl-G,-G R1, and in the leftward shift (figures going to higher positions), it changes to Rl-R-G -G -G -FAS-Rl. During indication, the content of R1 circulating in the loop Rl-G -G -G -FAs-Rl is indicated in the indicator. Such a change of the circulation loop is accomplished through the control of gates 0,, G and G The shift control of the decimal point register RlP is performed by clock pulses supplied to this register. Namely, a shift to the right of the content of the indication register R1 decreases the content of the decimal point register RIP by one and a shift to the left increases the content by one.

In FIG. lb, the first indication register is doubled. Namely, a register RlA corresponds to R1 of FIG. la and another auxiliary register RIB is provided for temporarily storing figures which have overflowed from the register RlA. Reference marks G G G G represent shift gates, and RlAP, R2BP decimal point registers. Other reference marks represent similar parts represented by similar reference marks shown in FIG. la. The shift control of numerical information is performed in registers RlA and RIB. Namely, the content of the registers RIA and RIB normally circulates in the loop of R1A-G -G -G -G.,-FAS-RlB-RlA, in the rightward shift in the loop of RlA-G -G -G -RlB-RlA, and in the leftward shift in the loop of RlA-R0-G -G G -G -FAS-R1B-R1A. Since registers RlA and RIB form a register of double length in this example, the content of R2 may circulate twice during one circulation cycle of the content of RlA and RIB. During indication, an information circulates in the loop of RlA- G -G -RlA and the content of only RlA is indicated in the indicator. Thus, among the set operands and the result of an operation, those other than included in RlA are overflowed or underflowed. In FIGS. 1a and 1b, arrows 11 and 12 shown by dotted lines indicate that the shift operation of the registers are performed through commands from discrimination elements indicated in a block 13.

FIGS. 2a to 2d show examples of how the contents of the registers change in actual operation by comparing a conventional automatic decimal point system capable of designating figures and the changing state of the contents of the registers according to the present invention (the number of indication figures is shown as fourteen). FIG. 2a shows the case in which the conventional system and the present system present the same indication. FIGS. 2b to 2d show the cases in which the conventional system causes overflow resulting in an invalidated operation, whereas the present system can indicate the result of an effective operation. More particularly, FIG. 2b shows the case in which the decimal point position of the resultant member coincides with the preselected decimal point position; FIG. 2c shows the case in which although the decimal point does not coincide with the preselected position, the upper fourteen figures are correctly shown; and FIG. 2d shows the case in which overflow has occurred in the operation step, but the result is correctly indicated.

As can be seen from the above examples, the conventional automatic decimal point system capable of setting the position of the decimal point causes overflow to invalidate the operation if 14 the position of preselected decimal point the number of integral figures of the resultant number, whereas the present system can indicate the result of the operation correctly within 14 figures unless 14 the number of integral figures of the resultant number in addition to a function identical with that of the conventional system, thereby doubling the operation function. Further, according to the conventional system, overflow may occur in the step of adjusting the decimal point position of operands to invalidate all the further operation, but the present system eliminates such drawbacks. Thus, the present system is particularly useful for calculations in engineering involving numbers of many figures in which the upper figures of the result are important. For ordinary business calculations dealing with numbers of smaller figures, this system provides the result with the preset decimal point position similar to the conventional system.

Now, decimal point processing in'the case of the two register type apparatus of FIG. 1a will be described referring to FIGS. 3a to 36, in which routes shown by solid lines indicate the conventional operations and those shown by dotted lines indicate those of the present invention. Hexagonal blocks represent discrimination elements and rectangular blocks show a control operation based on the results of discrimination. The number of the indication positions is assumed to be 14. Indices used in the drawings represent the following:

N; number key,

P; decimal point key,

R l; indication register,

R1 fourteenth position (the highest position) of the register R1,

R2; auxiliary register,

RIP; register for memorizing the decimal point position of the content of RI,

R2P; register for memorizing the decimal point position of the content of R2,

FAS; adder,

FF flipflop for memorizing that the decimal point key is pressed,

R] X I0; shifting the content of R1 to the left by one position,

R1 X 10'; shifting the content of Rl to the right by one position,

RIP +1; adding one to the content of R l P,

RIP l; subtracting one from the content of RIP, and

FF; selected decimal point position (capable of being arbitrarily preset within fourteen positions).

In FIG. 3a, when a number key N or a decimal point key P is pressed in the step of setting numbers, the discrimination whether it is N or P is performed. If it is P, FF, is set, and if it is N, only the registering of a number or the registering of a number and the decimal point addition are performed according to whether FF, is already set or not.

According to the conventional system, decimal point processing is completed by the above process, and each time a number key is pressed, a number is sequentially registered from the lowest figure position of R1 to a higher position, and when the number being registered exceeds 14 figures, overflow occurs from the highest position.

Whereas, according to the present system, owing to the added routine shown by the dotted lines, when a number exceeding 14 figures is registered, a numeral which has been in the highest figure in R1 is temporarily shifted into FAS to break the conditions of both FAS 0 and RIP 14. This state is automatically detected to cause a rightward shift by one figure of the content of RI and RIP. Thus, the numeral which has been in the lowest figure is removed and the numeral memorized in FAS is returned to the highest figure position of RI. Accordingly, any numerals beyond the 14th figure are prevented from entering the register.

FIGS. 3b and 3c show the flow of decimal point processing after the registering of numbers to the end of the operation taking the case of addition as an example.

The adjustment of the decimal points of the addend and the augend is performed in the steps l to 5.

In step 1, according to the conventional system, only the contents of RIP and R2P are compared. And, in the case of R2P RIP, the content of R1 is shifted to higher positions until the condition of R2P RIP is satisfied. If the condition either FAS 0 or RIP 9* 14 is not met, it leads to overflow. Whereas, according to the present system, the conditions of R1 0 and FAS 0 are added to the requirement for the leftward shift of the content of R1. When all of the conditions R1,.

0, FAS 0 and R2P RIP are satisfied, the content of R1 is shifted to a higher position and l is added to the content of RIP. In the case of RI 0, the operation goes to the next step without shifting the content of R1 to a higher position, even if RZP RIP.

In step 2, the contents of'RI and R2 and those of RIP and R2P are exchanged with each other in both systems.

In step 3, a similar process to that of step 1 is performed for the exchanged content of R1. Namely, according to the conventional system, if only the condition R2P RIP is satisfied, the operations R1 X 10 and RIP l are repeated, and if not, then the operation goes to the next step. Unless the condition of FAS 0 and RIP 9* 14 are met as a result of a leftward shift, overflow is caused.

In step 4, the contents of RI and R2 and those of RIP and R2P are again exchanged.

Step 5 is necessary only for the present system, wherein the condition which has not been met in steps I and 3 is re-checked. If RIP R2P, the content of R1 is shifted to a lower position and the content of RIP is subtracted by one to satisfy RIP R2P. The conventional system does not need this step since whether the condition is satisfied or overflow occurs is determined in steps 1 and 3.

- To assist understanding in what step the adjustment of decimal point positions is performed in the example shown in FIGS. 2a to 2d, the following table is shown.

Example Conventional Present System (I) step 1 step I (2) step l (OVF) stcpl step 3 (UNF) (3) stcp3(OVF) stcp3 stcpS (UNF) step 3 step 3 Here, OVF represents overflow and UNF underflow.

In step 6, the operation of addition is carried out in both systems. When carry takes place from the highest position of RI, a state of FAS l, i.e. overflow, is caused. The conventional system treats such a case as the invalidation of an operation.

Steps 7 and 8 are provided for making the RIP (the decimal point position of the result of an operation) coincide with FP (the preselected position of the decimal point).

According to the conventional system, if FP RIP, the adjustment of figures ofRI X 10 and RIP l is performed in step 7, and if FP RIP, that of RI X 10- and RIP I in step 8. As a result, the content of RI causes overflow in some cases.

According to the present system, the conditions RI 0 and FAS O are added to the conditions required for a shift in step 7 and FAS 9* 0 is added as the one in step 8. In step 7, unless all of the conditions, R1 0, FAS 0 and PP RIP, are satisfied, the operation goes to the next step without carrying out any leftward shift in the content of RI. And if FAS a 0, the operations RI X l0 and RIP l are performed in step 8 to remove the lowest figure and to introduce the highest figure (which has overflowed in step 6) stored in FAS into the highest position of R1. Thus, there exist some cases in which the decimal point position of the resultant number does not coincide with the preselected decimal point position as shown in the preceding operation examples, but there are no cases in which the operation becomes invalid by the reason'of overflow. There exist only such cases where RIP 0 holds, i.e., integral figures of the resultant number causes underflow to thereby invalidate the operation. Such cases can be indicated by lamp indication, etc. as will be apparent to those skilled in the art. (Even in such cases, the upper 14 figures can be read out.)

A description has been made on the case of addition hereinbefore. However, it will be apparent that decimal point processing in the case of subtraction can be similarly performed. Also in multiplication or division, the resultant number is prevented from overflow by passing through steps 7 and 8 after the product or the quotient is calculated via the same routes as in the conventional system.

Each of the discrimination elements indicated in the flowcharts can be easily constituted by employing a known checking circuit and a comparing circuit and logically combining their outputs by utilizing the techniques common to the art.

In the case of the three register type shown-in FIG. lb, FAS 0, R1 0 and RIP 14 are replaced by RIB O, RIA 0 and RIAP 14 respectively, takcapacity of the three register type is doubled as compared with that of the two register type.

As described above, this invention provides an electronic desk-top calculator convenient for calculations in both business and engineering, eliminating the drawbacks of the conventional decimal point processing system.

I claim:

1. In a calculator including an indication register for storing one operand or a resultant number, an auxiliary register for storing the other operand, and first and second decimal point registers respectively storing the decimal point positions of the operands in said indication and auxiliary registers, said one operand being registered from the lowest figure position of said indication register and the decimal point position of the resultant number being adjusted,

a decimal point processing system comprising:

first means, responsive to the contents of said indication and auxiliary registers, for detecting whether the position occupied by the highest figure of the operand having the lower decimal point position is the highest position of the register storing that operand,

second means, responsive to said first means and the contents of said decimal point registers, for adjusting, toward a higher position, the operand having the lower decimal point position until the highest position of that register is occupied or until the contents of said decimal point registers coincide,

third means, responsive to the contents of said indication and auxiliary registers, and said decimal point registers, for shifting the figure position of the operand having the higher decimal point position until the decimal point position of the number having the higher decimal point position is made to coincide with that of the number having the lower decimal point position,

fourth means, responsive to the contents of said indication register, for adjusting the position of the resultant number in accordance with a preselected decimal point position until the number occupies the higher position, so long as the highest position of the indication register is not occupied,

fifth means, responsive to the contents of said indication register, for temporarily storing overflowed numerals when the resultant number overflows from the indication register, and

sixth means, coupled to said fifth means and said indication register, for detecting the overflow of said resultant number and effecting a shift of the resultant number to a lower figure position;

thereby preventing the invalidation of operations due to overflow and indicating upper figures with a preference thereto.

2. A decimal point processing system according to claim 1, further comprising an adder for adding operands registered in said indication register and said auxiliary register and supplying the resultant number to said indication register, the adder being also utilized as said fifth means for temporarily storing the overflowed numerals.

3. A decimal point processing system according to claim 1, further comprising another auxiliary register connected to the highest figure position of said indication register and constituting a double length register with said indication register, said another auxiliary register being utilized as said fifth means for temporarily storing the numerals overflowed from the indication register.

4. A decimal point processing system according to claim 1, further comprising means, coupled to said indication register, for temporarily storing overflowed numerals when an operand to be registered overflows from the indication register in the step of registering operands therein and means for detecting the overflow of said operand and commanding a shift of said operand to a lower figure position.

5. In conjunction with a calculator including an indication register for storing an operand or a resultant number, an auxiliary register for storing another operand, and first and second decimal point registers respectively storing the decimal point positions of the operands in said indication and auxiliary registers, a process for setting the decimal point position in a mathematical operation on said operands comprising the steps of detecting whether the position occupied by the highest figure of the operand having the lower decimal point position is the highest position of the register storing that operand, adjusting toward a higher position the operand having the lower decimal point position if the highest position of said register is not occupied until said highest position is occupied or until coincidence of the contents of said decimal point registers occurs,

shifting the operand having the higher decimal point position toward a lower position until the decimal point positions of the two operands are made to coincide, and

performing said mathematical operation.

6. The process as defined in claim 5, further including the steps subsequent to performing said mathematical operation of detecting whether the highest figure of the resultant number of said mathematical operation is the highest position of the indication register, and

adjusting the position of the resultant number to a pre-selected decimal point position so long as the highest position of the indication register is not occupied.

7. The process as defined in claim 6, further including the steps of temporarily storing during the performing of said mathematical operation numerals overflowing said indication register,

detecting the overflow of said resultant number,

shifting said resultant number to a lower figure position by a number of positions equal to the number of numerals which have been stored, and

shifting the temporarily stored numerals back into the available positions in said indication register.

8. The process defined in claim 5, wherein said adjusting step includes shifting the operand having the lower decimal point position one position toward a higher position, detecting whether the position occupied by the highest figure of the operand having the lower decimal point position is the highest position of the register storing that operand, and repeating these shifting and detecting steps until the highest position is occupied or until the contents of said decimal point registers coincide.

9. The process defined in claim wherein said shifting step includes shifting the operand having the higher decimal point position by one position, comparing the decimal point positions stored in said first and second registers, and repeating these steps until the decimal point positions of the two operands coincide.

10. The process as defined in claim 5, further includl0 ing the steps of 

1. In a calculator including an indication register for storing one operand or a resultant number, an auxiliary register for storing the other operand, and first and second decimal point registers respectively storing the decimal point positions of the operands in said indication and auxiliary registers, said one operand being registered from the lowest figure position of said indication register and the decimal point position of the resultant number being adjusted, a decimal point processing system comprising: first means, responsive to the contents of said indication and auxiliary registers, for detecting whether the position occupied by the highest figure of the operand having the lower decimal point position is the highest position of the register storing that operand, second means, responsive to said first means and the contents of said decimal point registers, for adjusting, toward a higher position, the operand having the lower decimal point position until the highest position of that register is occupied or until the contents of said decimal point registers coincide, third means, responsive to the contents of said indication and auxiliary registers, and said decimal point registers, for shifting the figure position of the operand having the higher decimal point position until the decimal point position of the number having the higher decimal point position is made to coincide with that of the number having the lower decimal point position, fourth means, responsive to the contents of said indication register, for adjusting the position of the resultant number in accordance with a preselected decimal point position until the number Occupies the higher position, so long as the highest position of the indication register is not occupied, fifth means, responsive to the contents of said indication register, for temporarily storing overflowed numerals when the resultant number overflows from the indication register, and sixth means, coupled to said fifth means and said indication register, for detecting the overflow of said resultant number and effecting a shift of the resultant number to a lower figure position; thereby preventing the invalidation of operations due to overflow and indicating upper figures with a preference thereto.
 2. A decimal point processing system according to claim 1, further comprising an adder for adding operands registered in said indication register and said auxiliary register and supplying the resultant number to said indication register, the adder being also utilized as said fifth means for temporarily storing the overflowed numerals.
 3. A decimal point processing system according to claim 1, further comprising another auxiliary register connected to the highest figure position of said indication register and constituting a double length register with said indication register, said another auxiliary register being utilized as said fifth means for temporarily storing the numerals overflowed from the indication register.
 4. A decimal point processing system according to claim 1, further comprising means, coupled to said indication register, for temporarily storing overflowed numerals when an operand to be registered overflows from the indication register in the step of registering operands therein and means for detecting the overflow of said operand and commanding a shift of said operand to a lower figure position.
 5. In conjunction with a calculator including an indication register for storing an operand or a resultant number, an auxiliary register for storing another operand, and first and second decimal point registers respectively storing the decimal point positions of the operands in said indication and auxiliary registers, a process for setting the decimal point position in a mathematical operation on said operands comprising the steps of detecting whether the position occupied by the highest figure of the operand having the lower decimal point position is the highest position of the register storing that operand, adjusting toward a higher position the operand having the lower decimal point position if the highest position of said register is not occupied until said highest position is occupied or until coincidence of the contents of said decimal point registers occurs, shifting the operand having the higher decimal point position toward a lower position until the decimal point positions of the two operands are made to coincide, and performing said mathematical operation.
 6. The process as defined in claim 5, further including the steps subsequent to performing said mathematical operation of detecting whether the highest figure of the resultant number of said mathematical operation is the highest position of the indication register, and adjusting the position of the resultant number to a pre-selected decimal point position so long as the highest position of the indication register is not occupied.
 7. The process as defined in claim 6, further including the steps of temporarily storing during the performing of said mathematical operation numerals overflowing said indication register, detecting the overflow of said resultant number, shifting said resultant number to a lower figure position by a number of positions equal to the number of numerals which have been stored, and shifting the temporarily stored numerals back into the available positions in said indication register.
 8. The process defined in claim 5, wherein said adjusting step includes shifting the operand having the lower decimal point position one position toward a higher position, detecting whether the position occupied by the highest figure oF the operand having the lower decimal point position is the highest position of the register storing that operand, and repeating these shifting and detecting steps until the highest position is occupied or until the contents of said decimal point registers coincide.
 9. The process defined in claim 5 wherein said shifting step includes shifting the operand having the higher decimal point position by one position, comparing the decimal point positions stored in said first and second registers, and repeating these steps until the decimal point positions of the two operands coincide.
 10. The process as defined in claim 5, further including the steps of temporarily storing during the performing of said mathematical operation numerals overflowing said indication register, detecting the overflow of said resultant number, shifting said resultant number to a lower figure position by a number of positions equal to the number of numerals which have been stored, and shifting the temporarily stored numerals back into the available positions in said indication register. 